System and method for enhancing computer-generated images of terrain on aircraft displays

ABSTRACT

A system and method are disclosed for enhancing the visibility and ensuring the correctness of terrain and navigation information on aircraft displays, such as, for example, continuous, three-dimensional perspective view aircraft displays conformal to the visual environment. More specifically, an aircraft display system is disclosed that includes a processing unit, a navigation system, a database for storing high resolution terrain data, a graphics display generator, and a visual display. One or more independent, higher precision databases with localized position data, such as navigation data or position data is onboard. Also, one or more onboard vision sensor systems associated with the navigation system provides real-time spatial position data for display, and one or more data links is available to receive precision spatial position data from ground-based stations. Essentially, before terrain and navigational objects (e.g., runways) are displayed, a real-time correction and augmentation of the terrain data is performed for those regions that are relevant and/or critical to flight operations, in order to ensure that the correct terrain data is displayed with the highest possible integrity. These corrections and augmentations performed are based upon higher precision, but localized onboard data, such as navigational object data, sensor data, or up-linked data from ground stations. Whenever discrepancies exist, terrain data having a lower integrity can be corrected in real-time using data from a source having higher integrity data. A predictive data loading approach is used, which substantially reduces computational workload and thus enables the processing unit to perform such augmentation and correction operations in real-time.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of U.S. patent application Ser. No. 11/169,451, filedJun. 29, 2005.

FIELD OF THE INVENTION

The present invention relates generally to the field of display systems,and more specifically, but not exclusively, to a system and method forenhancing computer-generated images of terrain on aircraft displays.

BACKGROUND OF THE INVENTION

Modern aircraft contain visual display systems that provide flight crewswith substantial amounts of important operational and situationalawareness information about the environment outside the aircraft, suchas terrain. In fact, multi-functional aircraft displays that provideflight crews with computer-enhanced, three-dimensional perspectiveimages of terrain (e.g., especially during conditions of low visibility)are known. One approach used to enhance terrain imagery in existingmulti-functional aircraft displays is to combine high resolution,computer-generated terrain image data derived from onboard databases(e.g., synthetic vision systems) with enhanced, real-time terrain imagedata derived from onboard vision sensor systems (e.g., Forward LookingInfrared/FLIR sensors, active and passive radar devices, etc.). However,a major drawback of this approach is that significant data integrityissues exist with the computer-generated terrain information derivedfrom the onboard databases, and significant non-intuitive imaging issuesexist with the real-time terrain information derived from the visionsensor systems. Also, similar issues may arise in other applications.For example, data integrity and imaging issues can arise with the use ofsynthetic vision displays for Unmanned Aerial Vehicle (UAV) operations,and high-fidelity flight training simulators using flight worthy datasources where certain targets or objects are mapped with higher accuracythan the underlying terrain. As a result of these problems, visualdisplay disparities and operator errors can occur.

For example, in today's aircraft displays, high resolution terrain datahas to be provided on a continuous basis to an onboard graphics displayprocessor, in order for the processor to produce steady,three-dimensional perspective view images of the terrain for criticalflight applications. However, since terrain data for aircraftapplications typically covers the entire globe on a continuous basis,such an onboard database would contain an enormous amount of terraindata. Thus, it would be an almost impossible task to physically verifyall of the data points in such a database for critical flightapplications. As such, other techniques are required to correct andaugment this data, and especially during the operational phases wherethe terrain information is important for flight applications, such asduring take-offs and landings or near terrain-challenged areas.Additionally, the techniques used for data correction and augmentationneed to lead to information presented to flight crews in correct andnatural formats so as not to introduce additional confusion factorsduring the critical phases of flight operations. Generally, real-timedata correction and augmentation techniques need to be performed inthose applications where the terrain information displayed has moreimpact for flight operations, and where other data from more accuratesources (e.g., localized databases, real-time sensors, uplinks fromground-based databases, etc.) are available.

Another significant problem with the use of high resolution terrain datafor these perspective view display applications is that they place aheavy load on the processor involved, and therefore, certain datacomputation techniques (e.g., simple- or continuous-level of detailcomputation techniques) have to be used in order to reduce thecomputational workload. Additionally, the terrain data is alsodecompressed and dynamically displayed. Consequently, using the existingdata computation techniques, whenever a large patch of terrain data isloaded for pre-processing during the initialization phase (e.g.,immediately after the terrain display application is turned on), theprocessing system experiences a significant latency period and acorresponding delay before that data can be displayed. Similarly, usingexisting data computation techniques, if the processing system attemptsto load such terrain data in real-time, then significant discontinuitiesand instabilities can occur with the display of the data derived fromregions close to the borders of previously loaded data. As such, thesedata integrity and processing problems impose significant data storageand processing limitations on existing onboard aircraft display systems,which significantly limit the usefulness of displays for flight criticalapplications. Since it is impractical to completely verify all of thedata stored in the database, a viable data computation technique isneeded that will enable a processor to produce steady, perspective viewimages of terrain information for critical flight applications, wherebythe terrain information is derived from the fusion of high resolutionterrain data retrieved from a database, with real-time data receivedfrom one or more vision sensor systems, an onboard database havinghigher data precision in localized areas, one or more radar sensors, orprecision data uplink from one or more ground stations. In any event, anexample of the above-described data computation problem is illustratedby FIG. 1, which depicts an existing computer-generated aircraftdisplay.

Referring to FIG. 1, display 100 represents a conventional onboardelectronic display, such as, for example, a Primary Flight Display (PFD)and/or a Heads-Down Display (HDD). Display 100 shows, among otherthings, computer-generated symbols representing a zero pitch referenceline 102, a flight path marker (also known as a flight path vector, orvelocity vector) 104, an airspeed scale or tape 106, an altitude scaleor tape 108, and natural terrain (e.g., identified generally as element110). Essentially, as an aircraft approaches an airport (e.g., man-madeterrain feature) for landing, the pilot locates an intended runway(e.g., also man-made terrain feature), and aims the aircraft in thedirection of the runway. The pilot aims the aircraft at the runway bycontrolling the aircraft's movement, which typically results in therunway remaining in the close vicinity of the flight path marker symbol104. However, as illustrated by the example shown in FIG. 1, a runwaysymbol is not being displayed, although it may be assumed that the arrow112 identifies the known location of a runway relative to this view. Inthis case, the elevation of the terrain data that produces thecomputer-generated three-dimensional image (e.g., of natural terrain110) is slightly higher than the elevation of the runway data (e.g., forthe man-made terrain/runway at location 112). Thus, due to theaforementioned problems with the existing data computation techniquesused, the symbol for the runway known to be at location 112 is obscuredon conventional display 100. As such, this loss of visual contact ofsuch critical runway/terrain information by a pilot (e.g., especially inthe vicinity of that airport) decreases the effectiveness, accuracy andsafety of the flight decisions being made, and thus increases thepossibility that dangerous flight management, navigation or controlerrors can occur. Therefore, it would be advantageous to have a systemand method that enhances computer-generated terrain images on anelectronic display, such as, for example, a PFD, HDD, or similarelectronic aircraft display. As described in detail below, the presentinvention provides such a system and method, which resolves the terraindata integrity problems, data computation problems, and terrainvisibility problems encountered with existing electronic aircraftdisplays.

SUMMARY OF THE INVENTION

The present invention provides an improved system and method forenhancing the visibility of terrain and navigation information onaircraft displays, such as, for example, continuous, three-dimensionalperspective view aircraft displays conformal to the visual environment.In accordance with a preferred embodiment of the present invention, anaircraft display system is provided that includes a processing unit, anavigation system, a database for storing high resolution terrain data,a graphics display generator, and a visual display. One or moreindependent, higher precision databases with localized position data,such as navigation data or position data is onboard. One or more onboardvision sensor systems associated with the navigation system providereal-time spatial position data for display. One or more data links isavailable to receive precision spatial position data from ground-basedstations. The processing unit directs the graphics display generator togenerate graphic control signals for the visual display, which enhancethe visibility of the terrain and navigational information shown on thecontinuous, three-dimensional perspective view display. Essentially,before terrain and navigational objects (e.g., runways) are displayed, areal-time correction and augmentation of the terrain data is performedfor those regions that are relevant and/or critical to flightoperations, in order to ensure that the correct terrain data isdisplayed with the highest possible integrity. These corrections andaugmentations performed are based upon higher precision, but localizedonboard data, such as navigational object data, sensor data, orup-linked data from ground stations. Whenever discrepancies exist,terrain data having a lower integrity can be corrected in real-timeusing data from a source having higher integrity data. A predictive dataloading approach is used to allow such real-time operations, whereby theprocessing unit determines an aircraft's current position, heading andspeed, and initially loads a patch of terrain data for a region that issuitably sized to provide a rapid initialization of the data, datacorrections, and for a reasonable amount of flight time. The processingunit then monitors the aircraft's position, heading and speed, andcontinuously predicts the potential boundaries of a three-dimensionalregion or volume of terrain in the flight path based on the aircraft'sposition, heading and speed. The processing unit compares the predictedboundaries with the boundaries of the initially loaded terrain data, andif the distance from the aircraft to a predicted boundary is determinedto be less than a predetermined value (e.g., associated with theboundaries of the initially loaded data), then the processing unit loadsa new patch of terrain data that is optimally sized given the aircraft'scurrent position, heading and speed. In order to minimize the durationof the pre-processing operation prior to loading the new patch ofterrain data, the processing unit compiles the new patch of terrain datapartially with old data derived from the previously loaded patch andalso new data retrieved from the database.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself, however, as well asa preferred mode of use, further objectives and advantages thereof, willbest be understood by reference to the following detailed description ofan illustrative embodiment when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 depicts an existing computer-generated aircraft display;

FIG. 2 depicts a block diagram of an example system for ensuring thecorrectness of terrain information on an aircraft display, which can beused to implement a preferred embodiment of the present invention;

FIG. 3 depicts a pictorial representation of a visual display, whichillustrates the present invention's terrain data correction andaugmentation approach for producing enhanced and visually correctthree-dimensional perspective view displays;

FIG. 4 depicts a flow chart showing an exemplary method for performinglimited patch terrain data loading and correction based on high accuracyspatial position data to enhance the visibility and ensure thecorrectness of terrain information on an electronic display, inaccordance with a preferred embodiment of the present invention;

FIG. 5 depicts an illustrative example of a method for selecting a patchof terrain data for loading, in accordance with a preferred embodimentof the present invention;

FIG. 6 depicts an example of an enhanced display of runway data on anelectronic aircraft display, in accordance with a preferred embodimentof the present invention; and

FIG. 7 depicts an illustrative example of an enhanced display of terraindata and augmentation with high accuracy spatial position data wherethere is a discrepancy in the data involved.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

With reference again to the figures, FIG. 2 depicts a block diagram ofan example system 200 for ensuring the correctness of terraininformation on an aircraft display (e.g., continuous, three-dimensionalperspective view display), which can be used to implement a preferredembodiment of the present invention. For this example, system 200includes a processing unit 202, a database 204, a navigation system 206,a high speed data link 207, a graphics display generator 208, a visualdisplay 210, and one or more vision sensor systems 212. Notably, itshould be understood that although system 200 appears in FIG. 2 to bearranged as an integrated system, the present invention is not intendedto be so limited and can also include an arrangement whereby one or moreof processing unit 202, database 204, navigation system 206, data link207, graphics display generator 208, visual display 210 and one or morevision sensor systems 212 is a separate component or a subcomponent ofanother system located either onboard or external to an aircraft. Also,for example, system 200 can be arranged as an integrated system (e.g.,aircraft display system, PFD system, etc.) or a subsystem of a morecomprehensive aircraft system (e.g., Flight Management System,navigation and control system, target aiming and control system,collision alert and/or avoidance system, weather avoidance system,etc.).

For this embodiment, processing unit 202 can be a computer processorsuch as, for example, a microprocessor, digital signal processor, or anysuitable processor capable of at least receiving and/or retrievingaircraft status information, real-time terrain information andnavigation and control information (e.g., from navigation system 206and/or one or more vision sensor systems 212), and high resolutionterrain information (e.g., from database 204), and also generatingsuitable display control signals for a visual display of the aircraftstatus information, the navigation and control information (including,for example, a zero pitch reference line, heading indicators, tapes forairspeed and altitude, flight path marker or similar type of aircraftaiming symbol, etc.), the high resolution terrain information, and thereal-time terrain information, and sending the generated display controlsignals to a graphics display generator (e.g., graphics displaygenerator 208) associated with a visual display (e.g., visual display210).

For example, processing unit 202 can be arranged as a single processoror plurality of processors connected to a data communications bus orsystem bus. A memory controller/cache can also be connected to the datacommunications bus or system bus, which can provide an interface betweenprocessing unit 202 and a local memory (e.g., RAM, ROM, etc.).Preferably, but not necessarily, a high-speed data communications bus orsystem bus is used. A plurality of machine instructions can be stored inthe local memory and retrieved and operated on by processing unit 202 togenerate the control signals for the graphics display generator 208 andvisual display 210. An Input/Output (I/O) bus bridge can also beconnected to the data communications bus or system bus, which canprovide an interface between processing unit 202 and an I/O bus. Thus,processing unit 202 can receive, retrieve and/or send data via such anI/O bus. In any event, those of ordinary skill in the art willappreciate that the hardware described herein for processing unit 202 inFIG. 2 may vary. As such, the depicted example is provided forillustrative purposes and not meant to imply any architecturallimitations with respect to the present invention.

For this example embodiment, system 200 also includes database 204coupled to processing unit 202 (e.g., via an I/O bus connection). Forexample, database 204 can be a memory device (e.g., non-volatile memory,disk, drive, tape, optical storage device, mass storage device, etc.)that can store digital terrain data (e.g., latitudinal and longitudinaldata) as either absolute coordinate data or as a function of anaircraft's position. A source for the digital terrain data stored indatabase 204 can be, for example, a United States Geological Survey(USGS) map having a suitable resolution (e.g., approximately 90 meters),which includes topographical relief information that can be used toapply grid lines following the contour of terrain. Also, database 204can store a target location database that includes data defining theknown geographical boundaries of numerous airports and runways (e.g.,static, man-made terrain data).

Database 204 can also include, for example, a suitable terrain database,which can include the locations and elevations of natural terrainobstacles such as mountains or other elevated ground areas, and also thelocations and elevations of man-made obstacles such as radio antennatowers, buildings, bridges, etc. Such a terrain database can alsoinclude, for example, the boundaries of restricted airspace, restrictedelevations for particular airspace, bodies of water, etc. As yet anotherexample, a terrain database stored in database 204 can be aJeppesen-styled database, which can cover, for example, a 300 by 270mile area of terrain and include topographical relief information.Database 204 can also include a separate navigation database forlocalized targets, such as, for example, runways, navigationalwaypoints, and position beacons (e.g., very high accuracy data due tothe improved mapping and surveying techniques employed during theirlong-term and continuous use).

Notably, for this example embodiment, real-time airport and runwaylocation data and similar types of terrain data (e.g., spatial positiondata) are also received (e.g., by processing unit 202) from an onboarddevice 212 (e.g., vision sensor system that may or may not be associatedwith navigation system 206) that senses and maps man-made obstacles(e.g., airports, runways, etc.) and variations in natural terrain, suchas, for example, a FLIR sensor, or an active or passive type of radardevice. Also, in addition to the airport and runway location data, othertypes of high priority data (e.g., locations of incoming traffic toavoid, constructed waypoints, obstacles in the aircraft's flight path,etc.) can be retrieved and/or received by processing unit 202 from asuitable source of such data, such as, for example, an onboardnavigation database (e.g., a component of navigation system 206), anonboard FLIR sensor or radar device (e.g., a vision sensor system 212),or an external database via a data communication up-link (e.g., datalink 207). As such, this high priority data can include high precisionspatial position data.

For this embodiment, system 200 also includes navigation system 206coupled to processing unit 202 (e.g., via a respective I/O busconnection). Navigation system 206 can provide navigation dataassociated with the aircraft's current status, position and flightdirection (e.g., heading, course, track, attitude, etc.) to processingunit 202. As such, navigation system 206 can include, for example, aninertial navigation system, a satellite navigation system (e.g., GlobalPositioning System) receiver, VLF/OMEGA, Loran C, VOR/DME, DME/DME, IRS,aircraft attitude sensors, or the navigation information can come froman onboard Flight Management System (not shown). The navigation dataprovided to processing unit 202 can also include information about theaircraft's airspeed, altitude (e.g., relative to sea level), attitude,pitch, and other important flight information if such information isdesired. In any event, for this example embodiment, navigation system206 can include any suitable position and direction determinationdevices that are capable of providing processing unit 202 with at leastan aircraft's current position (e.g., in latitudinal and longitudinalform), the real-time direction (e.g., heading, course, track, etc.) ofthe aircraft in its flight path, and other important flight information(e.g., pitch, airspeed, altitude, attitude, etc.).

For this embodiment, system 200 also includes graphics display generator208 coupled to processing unit 202 (e.g., via an I/O bus connection) andvisual display 210. Visual display 210 can also be coupled to processingunit 202 (e.g., via an I/O bus connection). For example, visual display210 may include any device or apparatus suitable for displaying varioustypes of computer-generated symbols and information representing atleast natural and man-made terrain, pitch, heading, flight path,airspeed, altitude, attitude, target data, and flight path marker datain an integrated, multi-color or monochrome form (e.g., flat-panel colordisplay). Using an aircraft's current position, speed and direction(e.g., heading, course, track, etc.) data retrieved (or received) fromnavigation system 206, real-time terrain data retrieved (or received)from one or more vision sensor devices 212 (e.g., that may or may not beassociated with navigation system 206), and natural and man-made terraindata retrieved from database 204, processing unit 202 executes one ormore algorithms (e.g., implemented in software) for controlling theloading and pre-processing of terrain data for display using apredictive data loading approach (primarily to minimize computationworkload) based on the aircraft's current position, heading and speed.Processing unit 202 then generates a plurality of display controlsignals representing, among other things, the high resolution andreal-time terrain data received and/or retrieved, respectively, fromdatabase 204 and the vision sensor device(s) (e.g., vision sensor system212) associated with navigation system 206, and sends the plurality ofdisplay control signals to visual display 210 via graphics displaygenerator 208. Preferably, for this embodiment, visual display 210 is anaircraft cockpit, multi-color flat-panel display (e.g., a Primary FlightDisplay). Graphics display generator 208 interprets the receivedplurality of display control signals and generates suitable symbolsrepresenting the high resolution and real-time terrain data, along withsuitable symbols for the flight path marker, zero pitch reference line,heading indicator(s), airspeed tape, altitude tape, and targets, whichare presented on a screen or monitor of visual display 210.

Notably, although a conventional cockpit display screen may be used todisplay the above-described flight information and terrain symbols anddata, the present invention is not intended to be so limited and caninclude any suitable type of display medium capable of visuallypresenting multi-colored or monochrome flight information and terrainsymbols and data for a pilot or other flight crew member, and inparticular, but not exclusively, on a continuous, three-dimensionalperspective view aircraft display. As such, many known display monitorsare suitable for displaying such information, symbols and data, such as,for example, various CRT and flat-panel display systems (e.g., CRTdisplays, LCDs, OLED displays, plasma displays, projection displays,HDDs, Heads-Up Displays/HUDs, etc.). For example, visual display 210 canbe implemented as a heads-down Primary Flight Display by a DU-1080Display Unit or DU-1310 Display Unit, which are color active matrixLCD-based devices produced by Honeywell International, Inc. ofMorristown, N.J. Also, an example HUD that can be used for visualdisplay 210 is the HUD2020 device also produced by HoneywellInternational, Inc.

For this example embodiment, graphics display generator 208 can beconfigured to generate symbols representing terrain data, target data,aircraft status information, navigational information, and other flightinformation to a screen or monitor of visual display 210 (e.g.,responsive to operations of processing unit 202). For this embodiment,graphics display generator 208 (e.g., responsive to operations ofprocessing unit 202) may render a multi-colored or monochrome image ofnatural and man-made terrain, a flight path marker symbol, zero pitchreference line symbol, heading indicator symbols, airspeed and altitudetape symbols, and target symbols on a screen of visual display 210.Graphics display generator 208 (e.g., responsive to operations ofprocessing unit 202) may also render multi-colored or monochromaticimages of weather data on the screen of visual display 210.

Notably, in accordance with the principles of the present invention, thevisibility of the terrain information displayed on the screen of visualdisplay 210 may be enhanced responsive to one or more suitablealgorithms (e.g., implemented in software) executed by processing unit202, which functions to determine an aircraft's current position,heading and speed, and initially loads a patch of terrain data for aregion that is suitably sized to provide a rapid initialization of thedata, the data correction, and also sized for a reasonable amount offlight time. Processing unit 202 monitors the aircraft's position,heading, and speed (e.g., also attitude when pertinent), andcontinuously predicts the potential boundaries of a three-dimensionalregion (volume) of terrain in the flight path based on the aircraft'sthen-current position, heading and speed (e.g., and attitude whenpertinent). Processing unit 202 compares the predicted boundaries withthe boundaries of the initially loaded terrain data, and if the distancefrom the aircraft to a predicted boundary is determined to be less thana predetermined value (e.g., distance value associated with theboundaries of the initially loaded data), then processing unit 202initiates an operation to load a new patch of terrain data that isoptimally sized given the aircraft's current position, heading and speed(e.g., and attitude when pertinent). Also, processing unit 202 canfurther enhance the visibility of the terrain information beingdisplayed, by substituting real-time (and, for example, higher accuracy)terrain information (e.g., spatial position information) derived fromthe one or more onboard vision sensors (e.g., vision sensor system 212)for pertinent portions of the new data retrieved from database 204.Notably, for this example embodiment, processing unit 202 can executethe data loading operations separately from the operations thatdetermine the aircraft's current position, heading and speed, in orderto maintain a constant refresh rate and not interfere with thecontinuity of the current display of terrain. As such, FIG. 3 depicts apictorial representation of a visual display, which illustrates thepresent invention's terrain data correction and augmentation approachfor producing enhanced and visually correct three-dimensionalperspective view displays.

Referring to FIG. 3, a pictorial representation of a visual display 300(e.g., presentation for visual display 210 in FIG. 2) is shown, whichincludes a visual representation of an onboard aircraft display thatillustrates a preferred embodiment of the present invention. For thisexample embodiment, visual display 300 is preferably a heads-downPrimary Flight Display. However, the present invention is not intendedto be so limited and can also be implemented with any suitable type ofelectronic aircraft display (e.g., HUD) that can display, for example,continuous, three-dimensional perspective views of terrain informationand other important flight information (e.g., pitch, heading, course,track, airspeed, altitude, targets, aiming symbols, etc.). Essentially,an airport symbol can be displayed when an aircraft is higher than 1,000feet above ground level (AGL) or positioned at a significant distancefrom the airport involved, because the relative size of the airportmakes it visible from that altitude or distance. However, as theaircraft approaches the airport, a runway symbol should appear, and theairport symbol is typically removed from the display.

At this point it is important to note that, in accordance with thepredictive data loading and terrain visibility enhancement principles ofthe present invention, the view shown in visual display 300 differssignificantly from the view in prior art aircraft displays (e.g., visualdisplay 100 in FIG. 1), in that the airport runway information (e.g.,runway symbol 312) can now be seen in the view of visual display 300.This same runway information was obscured in the view of the prior artdisplay (e.g., visual display 100). Thus, for this example embodiment,when the aircraft is at a particular distance from the airport (e.g., ata much greater distance than that available using a conventionalthree-dimensional, perspective view display), the pilot can begincontrolling the aircraft so as to aim the aircraft at a selected portionof the runway 312, which results in the flight path marker (flight pathvector, velocity vector, aiming symbol, etc.) 304 remaining near theselected portion of the runway 312. As such, for this example, display300 also provides, among other things, a visual representation ofimportant flight, navigation and control information, such as a zeropitch reference line 302, an airspeed tape (or scale) 306, an altitudetape (or scale) 308, and natural terrain (e.g., identified generally aselement 310). Therefore, as illustrated by the view shown in FIG. 3, thepresent invention's predictive approach for loading relatively largeamounts of terrain data for a continuous, three-dimensional perspectiveview display, enhances the ability of the pilot to view (and also aimthe aircraft at) runway 312, which reduces pilot workload and navigationand control errors, and also results in increased flight safety.

FIG. 4 depicts a flow chart showing an exemplary method 400 forperforming limited patch terrain data loading and correction based onhigh accuracy spatial position data to enhance the visibility and ensurethe correctness of terrain information on an electronic display, inaccordance with a preferred embodiment of the present invention.Referring to FIGS. 2-4, for this example, processing unit 202 retrieves(or receives) current flight status information (e.g., current position,heading or track, speed) for an aircraft involved (step 402). For thisexample, the aircraft's current flight status information can beprovided by navigation system 206. Processing unit 202 then retrieves(e.g., from database 204) and loads an initial patch of terrain data,based on the aircraft's current position, heading and speed (step 404).The direction and size of the initial patch can also be based, forexample, on pertinent information derived from the aircraft's flightplan (e.g., intended flight path, etc.). An illustrative example of sucha patch of terrain data for loading is shown in FIG. 5.

Referring to FIG. 5, for this example embodiment, the region 500 canrepresent all (or a substantial portion of) the terrain informationstored in an onboard database (e.g., database 204) for an aircraftinvolved (e.g., represented by element 502) with respect to theaircraft's current position. In this example, a patch of terrain datafor loading is represented by the rectangular region (e.g., region 500)enclosing the triangular-shaped region, which is the terrain areacurrently being viewed by a flight crew (e.g., represented by element504) in FIG. 5. Notably, patch 504 of terrain data is formed of terraininformation that is directly in the flight path of aircraft 502.However, also note that although patch 504 is shown as a two-dimensionalregion in FIG. 5, it should be understood that this rendering is forillustrative purposes only, and for this embodiment, patch 504represents a three-dimensional region with a volume defined in twodimensions by the legs of the triangle and the enclosing rectangle, andwith the third dimension (perpendicular to the two-dimensional planedefined by the triangle) defined by the positive and negativeelevations. As such, for a second embodiment of the present invention, apatch of terrain data for loading can include, for example, some or allof region 500. In other words, the present invention is not intended tobe limited to a particular position, size or orientation for the patchof terrain data involved. However, for example, the position of thepatch selected for loading can be predetermined so as to offer areasonable flight time for augmentation or correction of the terraindata to be shown in the background, and the size of the patch selectedfor loading can depend on one or more of a number of pertinentparameters, such as the distance or range to the outermost edge of theview to be displayed in the direction of the flight path, the resolutionof the terrain data involved, and the processing speed required toaugment, and/or verify the integrity of, the terrain data selected forloading.

Returning to FIG. 4, for this example embodiment, processing unit 202then retrieves and loads high accuracy terrain data (e.g., for airports,runways, etc.) for a region that corresponds to patch 504 (step 406).For example, the high accuracy terrain data (e.g., spatial positiondata) can be retrieved (or received) from navigation system 206 (e.g.,with data generated by one or more vision sensor systems 212), directlyfrom one or more vision sensor systems 212, and/or from a pertinentground-based navigation system (e.g., via a data uplink connection 207).Next, for this example, processing unit 202 determines or selects asecond or new patch of terrain data to load (e.g., from database 204),based on the aircraft's current position, heading and speed (step 408).

Next, in order to reduce computational workload, processing unit 202limits the selected region of terrain data to a predetermined amount ofdata that will allow the computational process required to verify theintegrity of the terrain data involved to be completed relativelyquickly (step 410). Processing unit 202 then retrieves and loads thelimited region of terrain data which is located directly in the flightpath of the aircraft involved (step 412).

Next, in accordance with principles of the present invention, processingunit 202 executes one or more suitable algorithms (e.g., implemented insoftware) to verify the integrity of the retrieved terrain data (thelimited region) for one or more priority areas, such as, for example,for any region near to and including an airport, runway, etc. within thelimited region (step 414). Processing unit 202 then compares theaccuracy of the verified terrain data for the limited regions (e.g.,near airports, runways, etc.) with the accuracy of the high accuracyterrain data (e.g., precision spatial position data) retrieved earlierfor the same regions (step 416). If processing unit 202 determines thatthe high accuracy terrain data (e.g., precision spatial position data)for a priority region (e.g., airport, runway, etc.) is more accuratethan the verified terrain data for that same priority region (step 418),then processing unit 202 augments or corrects the verified terrain data(e.g., from database 204) for that priority region with the highaccuracy data (e.g., spatial position data from navigation system 206and/or one or more vision sensors 212) for that same region (step 420).Thus, in accordance with the present invention, the more accurateterrain information for the priority areas (e.g., airports, runways,etc.) derived from the available sources of terrain data (e.g., the highresolution data in the terrain database, or the high accuracy, spatialposition data from the navigation system, one or more vision sensors,data uplink, etc.) is now available for display, along with the highresolution terrain data for the remaining region outside the priorityregions.

However, if (at step 418) processing unit 202 determines that the highaccuracy terrain data for a priority region is not more accurate thanthe verified terrain data for that same priority region, then processingunit 202 determines if the verified terrain data (e.g., derived from thedatabase) for that priority region is significantly different than thehigh accuracy terrain data (e.g., derived from one or more vision sensorsystems 212, data uplink 207, and/or navigation system 206) for thatsame region (step 422). If processing unit 202 determines that theverified terrain data is significantly different than the high accuracyterrain data for a particular priority region (step 424), thenprocessing unit 202 determines if the difference between the verifieddata and high accuracy data is greater than a predetermined value (step426). If so, processing unit 202 can assume there is a significantdiscrepancy with that terrain data, and processing unit 202 can initiatea suitable algorithm to alert the flight crew (e.g., by display of avisual alert message and/or issuance of an audio alert message) of theterrain data discrepancy for the priority region(s) involved (step 428).The flight crew can then navigate without using that data on thedisplay. However, if (at step 424), processing unit 202 determines thatthe verified terrain data and high accuracy terrain data for the samepriority region(s) is/are not significantly different, then processingunit 202 forwards the verified terrain data (e.g., as augmented and/orcorrected with the high accuracy terrain data, spatial position data,precision spatial position data) to visual display 210 via graphicsdisplay generator 208 (step 430).

In accordance with a preferred embodiment of the present invention, anexample of an enhanced display of runway data on an electronic aircraftdisplay is shown in FIG. 6. As shown for this example embodiment, visualdisplay 600 includes terrain data for two runways 602 and other(natural) terrain data 604. The runways (602) are enhanced bysubstituting high accuracy terrain data (e.g., spatial position data)for the runways for the high resolution terrain data (e.g., terrain data604). Alternatively, in accordance with the present invention, FIG. 7illustrates an example of terrain data augmentation with high accuracydata where there is a discrepancy in the data involved. In this case,the runway data (702) on visual display 700 has been enhanced withrespect to the other terrain data (704), but inaccuracies with theintegrity of the high resolution airport data (706) have also beenenhanced. As such, for this example, the flight crew can visualize theproblem with this data discrepancy in visual display 700 and takecorrective action. However, the present invention also provides a visualand/or audio alert to notify the flight crew of such a data discrepancy.

Therefore, in accordance with the present invention, a system and methodare provided for enhancing the visibility and ensuring the correctnessof terrain information on an electronics aircraft display, in which highresolution terrain data for limited priority regions can be augmentedand/or corrected with high accuracy terrain data (e.g., spatial positiondata, precision spatial position data, etc.) for the same priorityregions, and the flight crew can be alerted to any discrepancy foundbetween the high resolution terrain data and high accuracy spatialposition data. For example, if the elevation of terrain data stored inan onboard database for a particular airport is slightly higher than theelevation of the terrain data for that airport derived from a navigationsystem, then that airport information can be obscured on a conventionaldisplay. However, the present invention can augment and/or correct theterrain data from the database with the more accurate spatial positiondata from the navigation system, which enhances the visibility andensures the correctness of the terrain data for priority regions (e.g.,near airports, runways, etc.) on the display. Nevertheless, if theterrain data about a known accurate data point is incorrect, then thatincorrect data can be amplified by the augmentation/correction process.Therefore, in accordance with the present invention, if the value of theaugmentation or correction of the terrain data is significantly greaterthan a predetermined or threshold value, then a visual and/or audioalert message regarding such a terrain data discrepancy can be issuedfor the flight crew. The flight crew can then decide whether or not tocontinue the approach based on direct visual navigation informationderived from another source (e.g., onboard sensor, Flight ManagementSystem, navigation system, GPS receiver, etc.).

It is important to note that while the present invention has beendescribed in the context of a fully functioning visual display system,those of ordinary skill in the art will appreciate that the processes ofthe present invention are capable of being distributed in the form of acomputer readable medium of instructions and a variety of forms and thatthe present invention applies equally regardless of the particular typeof signal bearing media actually used to carry out the distribution.Examples of computer readable media include recordable-type media, suchas a floppy disk, a hard disk drive, a RAM, CD-ROMs, DVD-ROMs, andtransmission-type media, such as digital and analog communicationslinks, wired or wireless communications links using transmission forms,such as, for example, radio frequency and light wave transmissions. Thecomputer readable media may take the form of coded formats that aredecoded for actual use in a particular visual display system.

The description of the present invention has been presented for purposesof illustration and description, and is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theseembodiments were chosen and described in order to best explain theprinciples of the invention, the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

1. A system for enhancing the visibility and ensuring the correctness ofterrain information on a visual display onboard an aircraft, comprising:a data storage unit, the data storage unit operable to store a set ofterrain data; a position data source, the position data source operableto produce a set of spatial position data; and a processing unit coupledto the data storage unit and the position data source, the processingunit operable to: receive at least one of a current position, headingand speed of the aircraft; load a patch of terrain data, the patch ofterrain data corresponding to a first region, the first region beingbased on at least one of the current position, heading and speed of theaircraft, and the patch of terrain data comprising a subset of the setof terrain data; identify a priority region within the first region;retrieve a subset of the set of spatial position data corresponding tothe priority region from the position data source; compare an accuracyvalue for a subset of the patch of terrain data corresponding to thepriority region with an accuracy value for the subset of the set ofspatial position data corresponding to the priority region; and augmentthe subset of the patch of terrain data corresponding to the priorityregion with the subset of the set of spatial position data correspondingto the priority region when the subset of the set of spatial positiondata is more accurate than the patch of terrain data.
 2. The system ofclaim 1, wherein the processing unit is operable to augment the subsetof the patch of terrain data by substituting at least a portion of thesubset of the set of spatial position data corresponding to the priorityregion for at least a portion of the subset of the patch of terraindata.
 3. The system of claim 1, wherein: the position data sourcecomprises a navigational database; and the set of spatial position datacomprises spatial position information derived from a plurality of datapoints stored in the navigational database.
 4. The system of claim 1,wherein: the position data source comprises a ground-based data-link;and the set of spatial position data comprises spatial positioninformation derived from the ground-based data-link, the spatialposition information characterizing at least one three-dimensionalspatial location for at least one data point of interest.
 5. The systemof claim 1, wherein the position data source comprises at least oneonboard real-time sensor, the set of spatial position data comprisingspatial position information derived from the at least one onboardreal-time sensor.
 6. The system of claim 1, wherein the set of spatialposition data further comprises at least one spatial position ofinterest, the at least one spatial position of interest including datarepresenting at least one of a navigation waypoint and a runway.
 7. Thesystem of claim 1, wherein the processing unit is operable to augmentthe subset of the patch of terrain data by performing a data correctionoperation, the data correction operation comprising an operation tocompare a plurality of runway end data points for the priority regionfrom a navigational database with the set of terrain data, and correctthe set of terrain data with the plurality of runway end data points. 8.The system of claim 1, wherein the processing unit is further operableto: generate a first plurality of control signals for the visualdisplay, the first plurality of control signals representing theaugmented patch of terrain data for the visual display.
 9. The system ofclaim 1, wherein the set of spatial position data is associated with theat least one of the current position, heading and speed and an attitudeof an aircraft.
 10. The system of claim 1, wherein the set of spatialposition data is selected from a group consisting of high precisiondata, high accuracy data, high priority data, and real-time data. 11.The system of claim 1, wherein the visual display is selected from agroup consisting of a Primary Flight Display, a Heads-Down Display, anda Heads-Up Display.
 12. The system of claim 1, wherein the processingunit is further operable to: limit the patch of terrain data so as tominimize a processing duration for verifying an integrity valueassociated with the patch of terrain data; verify the integrity valuefor the limited patch of terrain data; and load the limited patch ofterrain data.
 13. The system of claim 1, wherein the processing unit isfurther operable to: generate an alert message for display, if theaugmented patch of terrain data is substantially different than thepatch of terrain data.
 14. The system of claim 1, wherein the set ofspatial position data comprises a set of independent spatial positiondata including at least one of a subset of the set of terrain data orall of the set of terrain data.
 15. The system of claim 1, wherein theset of terrain data comprises high resolution terrain data.
 16. Thesystem of claim 1, wherein the set of spatial position data comprisesreal-time position data including at least one of a subset of the set ofterrain data and all of the set of terrain data.
 17. The system of claim1, wherein the set of terrain data comprises data stored in a terraindatabase.
 18. A system for an aircraft, the system comprising: a visualdisplay; a data storage unit to store terrain data for a priorityregion; a vision sensor system to obtain spatial position data for thepriority region; and a processing unit operable to: identify thepriority region based on current flight status information for theaircraft; determine the spatial position data for the priority region ismore accurate than the terrain data for the priority region; augment theterrain data for the priority region with the spatial position data inresponse to determining the spatial position data is more accurate; andprovide the augmented terrain data for the priority region to the visualdisplay.
 19. The system of claim 18, wherein: the vision sensor systemincludes one or more sensors onboard the aircraft; and the spatialposition data comprises real-time terrain information derived from theone or more sensors.
 20. A system for an aircraft, the systemcomprising: a visual display; a data storage unit to store terrain datafor a priority region; a position data source to obtain spatial positiondata for the priority region; and a processing unit operable to:identify the priority region based on current flight status informationfor the aircraft; determine the spatial position data for the priorityregion is more accurate than the terrain data for the priority region;augment the terrain data for the priority region with the spatialposition data in response to determining the spatial position data ismore accurate; and provide the augmented terrain data for the priorityregion to the visual display.